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P1851

Brake Band Apply Solenoid Performance.

  • Oldsmobile
  • Powertrain
  • Manufacturer code
  • Medium severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
8
AreaTransmission
51
FaultThe specific fault in that area

What it means

P1851 on an Oldsmobile means the transmission control module has detected a performance problem with the brake band apply solenoid in the automatic gearbox. The module saw the band apply behaviour, such as slip, flare or incorrect timing or pressure response, not match what it commanded. It is a GM-specific code and the exact gearbox and band layout depend on the model and transmission fitted.

Symptoms

  • Gearbox warning light or check engine light on
  • Harsh, delayed or flared gear changes
  • Slipping in a particular gear, or engine revving without matching acceleration
  • Transmission stuck in a fixed gear (limp mode)
  • Poor or inconsistent engagement when selecting a gear
  • Burnt smell from the transmission fluid

Possible causes

  • Low, degraded or contaminated transmission fluid affecting band apply pressurelikely
  • Faulty or sticking brake band apply solenoid, or a clogged internal filter or screenlikely
  • Damaged wiring, corroded terminals or poor connector contact at the solenoid or internal harnesspossible
  • Worn or burnt brake band, or a leaking servo or seals so the band cannot hold properlypossible
  • Valve body wear, sticking valves or internal pressure leakspossible
  • Fault in the transmission control module or its power and ground supplyrare

How to diagnose

  1. Read all stored and pending codes and note the freeze frame data, then check for other transmission or engine codes that may be related
  2. Check the transmission fluid level and condition against the manufacturer's procedure, looking for a burnt smell, dark colour or metal debris
  3. Inspect the wiring and connectors between the control module and the transmission, looking for chafing, fluid ingress, corrosion and bent pins
  4. Check the control module power and earth supplies and battery condition
  5. Measure the solenoid resistance and compare it with the specification for that model and gearbox
  6. Monitor commanded versus actual gear and slip data on a road test to see when the fault occurs
  7. Carry out a line pressure test to check band apply pressure against specification
  8. Drop the pan to inspect for debris and filter condition, and check the solenoid and valve body if the fault persists

How to fix

  • Correct the fluid level, or change the fluid and filter with the correct specification if it is degraded or contaminated
  • Replace the faulty brake band apply solenoid, or clean or replace the valve body components if they are sticking
  • Repair or replace damaged wiring, terminals or the internal harness connector
  • Overhaul or rebuild the transmission if the band, servo or seals are worn or leaking
  • Repair or replace the control module only after the supply, wiring and mechanical causes have been ruled out

Can I keep driving?

Medium severity

The car can usually be driven short distances to a workshop, but slipping can quickly damage the transmission, so avoid heavy loads and hard acceleration. If it slips badly or goes into limp mode, stop driving and get it recovered.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.

This code for other makes

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